Cardiovascular disease is now considered a major complication in the treatment of HIV. While a large number of clinical trials have examined the relationship between atherosclerosis and either the HIV infection or the antiretroviral treatment of HIV, no definitive cause-effect relationships have been observed. This may be due to the complex nature of HIV and its treatment in humans. We have developed a less complicated model to investigate the effects of antiretrovirals (ART) on the function of the vascular endothelium. Atherosclerosis, a disease characterized by cholesterol-laden plaque formation within the artery wall, is initiated by endothelial injury that results in the release of cytokines and growth factors. These growth factors promote a number of perpetuating events, such as vascular smooth muscle cell (VSMC) proliferation, that culminate in the formation of an atherosclerotic lesion. Thus, endothelial dysfunction is an early event and has been shown a sensitive marker for atherogenesis. In our initial studies using two rodent models for atherosclerosis, ART induced dramatic endothelial dysfunction within 5 days of treatment and chronic treatment exacerbated atherosclerotic lesion development. In addition, in endothelial cells in culture, ART induced mitochondrial dysfunction and increased the production of both reactive oxygen species (ROS) and the release of the mitogenic factor endothelin-1 (ET-1). Though the drugs had no apparent effect on VSMC alone, in cocultures of VSMC plus endothelial cells, the drugs increased VSMC proliferation in a manner dependent upon ET-1 receptor activation. We thus hypothesize that ART initiates or exacerbates atherogenesis by inducing a mitochondrial dysfunction in the vascular endothelium. Using both coculture systems of vascular cells and our mouse models for atherosclerosis, we will determine: 1) the contribution of mitochondrial dysfunction in ART-mediated endothelial dysfunction, 2) the contribution of reactive oxygen species production in ART-mediated endothelial dysfunction and ET-1 release, and 3) the mechanism by which ART promotes endothelium-derived ET-1 -induced vascular smooth muscle cell proliferation. LAY SUMMARY: Cardiovascular disease is now considered a major complication in HIV patients. These studies will help to address whether the drug therapy used to treat HIV is the cause of this HIV-related cardiovascular disease. The proposed work will thus be of clinical benefit in devising ways in which to better treat HIV-infected individuals.